Takashi Takeo

Measurement of Einstein's A Coefficient of the 296.7 nm Transition Line of the Carbon Atom

We measured Einsteins A coefficient of the transition line of the C atom at 296.7 nm (2s2p35S2 - 2s22p23P2), which is useful for the absorption spectrocopic measurement of C atom density in processing plasmas. Einsteins A coefficient was evaluated from the emission decay rate of the 296.7 nm line in an electron cyclotron plasma employing CO gas. The obtained value of 3.9×104 s-1 is almost 2000 times as large as the reported theoretical A coefficient [G. H. Garstang: The Observatory 82 (1962) 50].

Study on Transmission Characteristics of Transformers of a RF Splitter

In this paper, we report on the transmission characteristics of transformers of a RF splitter widely used in CATV systems. From the point of view of broadening the splitters operating frequency, the relationship between the RF transformers transmission characteristics and design parameters has been investigated using computer-aided engineering. Based on the calculations, a sample device has been fabricated to confirm the theoretical results. It has been found that the configulation of the transformer winding is the most important factor affecting device performance. By selecting the appropriate winding, excessive loss can be suppressed to less than 1.6 dB and 3 dB in a frequency range of 20 MHz to 2,600 MHz for the cases of 2-way and 4-way splitters, respectively.

Adaptive Compensation Method for the Temperature Dependence of RF Transformer Isolation

In this study, we propose an adaptive compensation method for the temperature dependence of RF transformer isolation and present results of preliminary experiments. First of all, we examine the isolation temperature dependence of an RF transformer designed as a splitter, by means of both an electromagnetic simulation technique and experiments, to show the significance of the present issue. Then, we discuss the nature of a transformer core so as to obtain the most desirable isolation characteristics against a temperature change. Finally, in order to adaptively compensate for the isolation variation due to temperature, we propose a bias current superimposed on the RF signal, where the current amplitude is adjusted according to temperature change, and demonstrate the results of preliminary experiments conducted at a fixed temperature, but with different bias currents, indicating the validity of the proposed method.

Optical Evaluation System for a Seaweed-Water Mixture in a Seaweed Processing Plant

An in-process optical measurement system has been proposed for a seaweed-water mixture in a seaweed processing plant with the aim of quality evaluation of final products. The system or method is based on the assumption that the optical transmissions of the mixture at particular wavelengths could be related to seaweed-product quality. In order to ascertain the above expectation, we have made measurements in a plant and done some analysis, including principal component analysis, on the measurement data. The results imply that the optical transmission data of the mixture can be used to estimate the quality of the final seaweed products. The information obtained could also be useful in making a feedback control of the process for producing better products.

Position Sensing and Communication System Using Fluorescent Doped Plastic Fiber

Various telecommunication techniques using supersonic, electromagnetic or light waves have been developed for application to remotely controlled machine operation systems, especially for microsystems. A light wave communication technique using fluorescent light in an optical fiber was considered to be applicable for this purpose. The fundamental communication properties of fluorescent-doped plastic fiber have been examined to realize such a system in a specific narrow space. As a result, the detectable distance of 5m with resolution of 5.6 mm and a communication rate of approximately 500 kbps was obtained.

Measurement of the Permeability in a Ferrite Core by Superimposing Bias Current

AbstractIn this study, we investigate measurement of the magnetic permeability in a ferrite core at RF frequencies when bias current is superimposed on an RF signal with a view to adaptively controlling performance of RF transformers using ferrite cores. A measurement arrangement used comprises a short microstrip line (MSL) circuit including a coaxial conductor (CC) structure consisting of an electrically grounded metal pipe, a center conductor and a sample between them. A bias tee network is incorporated into this MSL-CC circuit in order to superimpose direct current on an RF signal. Using this arrangement, a dependence of permeability on an amplitude of superimposed bias current was measured at frequencies of 10 MHz to 500 MHz. Reliability of the measurement results is discussed based on several experimental data, implying that the method has an accuracy less than 10% at most of the above frequencies.

Effectiveness of Magnetic Sheets in Suppressing Magnetic Leakage in Automobile Wireless Energy Transfer Systems

Recently, wireless energy transfer techniques are being developed for hybrid (HEV) or electric (EV) vehicles. However, without taking any measures, magnetic field strength around energy transfer systems that employ solenoid type antennas is known to exceed regulated values in most countries. In this study, the application of magnetic sheets, which are widely used as EMC components, is proposed to suppress the magnetic field leakage from an automobile energy transfer system and the ability of magnetic leakage suppression with the magnetic sheet has been evaluated by means of electromagnetic simulation. Through these investigations, desirable system arrangements are discussed. As a result, if combined with a metal plate, non-conductive magnetic materials having large permeability has been found to be preferable.

Simplified Method of Measuring Magnetic Permeability Temperature Profile for RF Device Applications

Ferrite is popular as a core material for RF transformers. Since transmission characteristics of RF transformers are affected by the core’s permeability, which has a large temperature dependence, the development of a method for measuring the core permeability temperature profile is important. In this study, a temperature profile measurement of ferrite core permeability has been investigated using a microstrip line method which has the advantage of the circuit being compact in size and therefore suitable for measuring temperature profiles. Based on the results measured with a sample ferrite core, the temperature dependence of RF transformer performance (isolation) is also discussed. Furthermore, basic results of experiments to compensate for the degradation in isolation is presented.

Development of a Super Broadband RF Splitter Using Bead Type Ferrite Core Transformers

We report on the broadening of the operating frequency of a RF splitter widely used in CATV systems. In order to realize this, the relationship between the splitter’s transmission characteristics and design parameters has been investigated using computer-aided engineering. Based on the calculations, a sample device has been fabricated to confirm the theoretical results. It has been found that by selecting the parameters appropriately, excessive loss can be suppressed to less than 1.6dB and 3dB in a frequency range of 20MHz to 2,600MHz in the cases of 2-way and 4-way splitters, respectively.